CN107181001B - Lithium ion secondary battery electrolyte additive, electrolyte and application thereof - Google Patents

Abstract

The invention discloses a lithium ion secondary battery electrolyte additive, electrolyte and application thereof, wherein an improved similar acrylic ester carbonate additive system and the electrolyte composed of the same are adopted, the lithium ion secondary battery electrolyte additive system is composed of two components, namely a similar acrylic ester carbonate compound A and a diisocyanate organic matter B, and a propylene ester carbonate derivative with a structure similar to that of PC is used for replacing PC to participate in the additive composition; the electrolyte additive system has clear components, the preparation method is simple, and the electrolyte additive is suitable for industrial application and has wide application prospects in the fields of power batteries and energy storage batteries.

Description

Lithium-ion secondary battery electrolyte additives, electrolytes and their applications

technical field

The invention relates to an electrolyte energy storage material for a lithium ion secondary battery and its application, in particular to an improved propylene carbonate-like additive system and a lithium ion battery electrolyte containing the additive system and its application. The field of secondary lithium-ion battery energy storage technology.

Background technique

Lithium-ion batteries have excellent comprehensive performance. With the development of mobile electronic devices, higher requirements have been placed on the energy density of lithium-ion batteries. This demand can be effectively met by increasing the working potential of lithium-ion batteries, but common carbonate solvents are easily decomposed at high voltages, resulting in a decrease in the discharge capacity of the battery. In the prior art, there is an onium polymerization film-forming mechanism composed of propylene carbonate (PC) and diisocyanate organic compounds, which can form a high-voltage stable passivation film on the surface of the positive electrode and improve the high-voltage cycle performance of the battery. However, the PC solvent is easily co-inserted with the graphite negative electrode in lithium-ion batteries, resulting in exfoliation and decomposition, which seriously reduces the capacity of the battery and deteriorates the high-voltage cycle performance of the lithium battery, which is not suitable for industrial applications.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior art, the object of the present invention is to overcome the deficiencies in the prior art, provide a lithium ion secondary battery electrolyte additive, electrolyte and application thereof, adopt an improved propylene carbonate-like additive system and its composition The electrolyte is composed of propylene carbonate derivatives similar in structure to PC instead of PC to participate in the additive composition, which effectively improves the high-voltage cycling performance of lithium batteries, and improves other high-potential electrochemical properties of the battery, and has no effect on the graphite negative electrode. adverse effects; the electrolyte additive system of the present invention has clear components, simple preparation method, is suitable for industrial application, and has wide application prospects in the field of power batteries and energy storage batteries.

To achieve the above object, the present invention adopts the following technical solutions:

A lithium ion secondary battery electrolyte additive system, which is composed of two components, a propylene carbonate-like compound A and a diisocyanate organic compound B, to form a lithium ion secondary battery electrolyte solution additive system, calculated based on the total weight of the electrolyte solution additive being 100%, The electrolyte additive contains 1-99 wt. % of propylene carbonate derivative A and 1-99 wt. % of diisocyanate-based organic substance B.

Preferably, the structural formula of the above-mentioned propylene carbonate-like compound A is:

In the structural formula, preferably R ₁ and R ₂ are each independently hydrogen, alkyl, alkenyl, alkoxy, aryl or cyano with a carbon content greater than 1, and when one of R ₁ and R ₂ is hydrogen , the other substituent is not hydrogen or methyl.

Preferably, the structural formula of the above-mentioned diisocyanate organic compound B is: R-[N=C=O]n, wherein, n≥2, preferably R is an alkyl bridging group with a carbon content greater than 1.

The above-mentioned propylene carbonate-like compound A preferably adopts ethylene ethylene carbonate (VEC), styrene carbonate or -2,3-butanediol carbonate; the diisocyanate-like organic substance B adopts hexamethylene diisocyanate; The mass ratio of propylene carbonate derivative A and diisocyanate organic compound B is (1-9):1.

An electrolyte containing the electrolyte additive for a lithium ion secondary battery of the present invention includes an electrolyte and a solvent, and the electrolyte contains a lithium salt and an electrolyte additive for a lithium ion secondary battery.

Above-mentioned solvent preferably adopts ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dimethyl sulfite, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate Ester, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate and propyl acetate, any single substance or a mixture of any of them.

Among the above electrolytes, the lithium salt is preferably any one of LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiODFB and LiN(SO ₂ CF ₃ ) ₂ or a mixed salt of any of them.

As a preferred technical solution of the present invention, based on the total mass of the electrolyte as 100%, the content of the electrolyte additive of the lithium ion secondary battery in the electrolyte is 0.002-10 wt.%.

As a further preferred technical solution of the present invention, the content of the lithium ion secondary battery electrolyte additive in the electrolyte is 5-10 wt.% based on the total mass of the electrolyte as 100%.

An application of the electrolyte of the present invention as the electrolyte of a lithium ion battery whose charging potential is not lower than 4.2V.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

1. The present invention provides an improved propylene carbonate-like additive combination, which can form a film on the surface of the positive electrode of the battery, hinder the further decomposition of the electrolyte, and effectively improve the cycle performance and rate performance of the lithium battery under high voltage;

2. The electrolyte additive system of the present invention has no negative impact on the performance of conventional graphite negative electrodes;

3. The electrolyte additive system of the present invention is in good agreement with the existing lithium-ion battery system, and does not need to replace the electrolyte, film, positive electrode material, and shell;

4. The electrolyte additive system of the present invention has clear components and a simple preparation method;

5. The electrolyte additive system of the present invention is suitable for industrial application and has broad application prospects in the fields of power batteries and energy storage batteries.

Detailed ways

Preferred embodiments of the present invention are described in detail as follows:

Example 1:

In the present embodiment, the preparation of the lithium ion secondary battery electrolyte additive 1 is carried out, specifically:

According to the mass ratio of VEC and HDI of 50:50 wt %, ethylene ethylene carbonate and HDI are mixed uniformly for use, and electrolyte additive 1 for lithium ion secondary battery is obtained.

Embodiment 2:

This embodiment is basically the same as the first embodiment, and the special features are:

In the present embodiment, the preparation of the lithium ion secondary battery electrolyte additive 2 is carried out, specifically:

According to the mass ratio of VEC and HDI of 70:30 wt %, ethylene ethylene carbonate and HDI are mixed uniformly for use, and electrolyte additive 2 for lithium ion secondary battery is obtained.

Embodiment three:

This embodiment is basically the same as the previous embodiment, and the special features are:

In the present embodiment, the preparation of the lithium ion secondary battery electrolyte additive 3 is carried out, specifically:

According to the mass ratio of styrene carbonate and HDI of 60:40 wt %, styrene carbonate and HDI are mixed uniformly for use, and electrolyte additive 3 for lithium ion secondary battery is obtained.

Embodiment 4:

This embodiment is basically the same as the previous embodiment, and the special features are:

In the present embodiment, the preparation of the lithium ion secondary battery electrolyte additive 4 is carried out, specifically:

According to the mass ratio of 2,3-butanediol carbonate and HDI of 90:10 wt %, the 2,3-butanediol carbonate and HDI are mixed uniformly for use, and electrolyte additive 4 for lithium ion secondary battery is obtained.

Embodiment 5:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of electrolyte 1 is carried out, specifically:

Measure the electrolyte HR-8335 (Shandong Hairong) in a glove box filled with high-purity argon, add the lithium ion secondary battery electrolyte additive 1 prepared in Example 1 to the electrolyte HR-8335, and mix Evenly, electrolyte 1 is prepared; in electrolyte 1, based on the mass of electrolyte 1 as 100%, the addition amount of electrolyte additive 1 for lithium ion secondary battery is 5% wt of electrolyte 1.

Embodiment 6:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of electrolyte 2 is carried out, specifically:

Measure the electrolyte HR-8335 (Shandong Hairong) in a glove box filled with high-purity argon, add the lithium ion secondary battery electrolyte additive 2 prepared in Example 2 to the electrolyte HR-8335, and mix Evenly, the electrolyte 2 is prepared; in the electrolyte 2, based on the mass of the electrolyte 2 as 100%, the addition amount of the electrolyte additive 2 of the lithium ion secondary battery is 10% wt of the electrolyte 2.

Embodiment 7:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of electrolyte 3 is carried out, specifically:

Measure the electrolyte HR-8335 (Shandong Hairong) in a glove box filled with high-purity argon, add the lithium ion secondary battery electrolyte additive 3 prepared in Example 3 to the electrolyte HR-8335, and mix Evenly, the electrolyte 3 is prepared; in the electrolyte 3, the amount of the electrolyte additive 3 of the lithium ion secondary battery is 7% wt of the electrolyte 3 based on the mass of the electrolyte 3 as 100%.

Embodiment 8:

This embodiment is basically the same as the previous embodiment, and the special features are:

In the present embodiment, the preparation of electrolyte 4 is carried out, specifically:

Measure EC and DMC with a mass ratio of 1:1 in a glove box filled with high-purity argon, mix them evenly to prepare a solvent, and then add the solute LiPF ₆ to a concentration of 1 mol/L of LiPF ₆ to prepare EC-DMC-LiPF ₆ Electrolyte system, then add the lithium ion secondary battery electrolyte additive 1 prepared in Example 1 to the EC-DMC-LiPF ₆ electrolyte system, mix well, and make electrolyte 4; In electrolyte 4, with When the mass of the electrolyte 4 is 100%, the addition amount of the electrolyte additive 1 for the lithium ion secondary battery is 5% wt of the mass of the electrolyte 4 .

Embodiment 9:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of electrolyte 5 is carried out, specifically:

Measure EC and DMC with a mass ratio of 1:1 in a glove box filled with high-purity argon, mix them evenly to prepare a solvent, and then add the solute LiPF ₆ to a concentration of 1 mol/L of LiPF ₆ to prepare EC-DMC-LiPF ₆ Electrolyte system, then add the lithium ion secondary battery electrolyte additive 3 prepared in Example 3 to the EC-DMC-LiPF ₆ electrolyte system, mix well, and make electrolyte 5; In electrolyte 5, with When the mass of the electrolyte 5 is 100%, the added amount of the electrolyte additive 3 for the lithium ion secondary battery is 5% by weight of the electrolyte 5 .

Embodiment ten:

This embodiment is basically the same as the previous embodiment, and the special features are:

In the present embodiment, the preparation of electrolyte 6 is carried out, specifically:

Measure EC and DMC with a mass ratio of 1:1 in a glove box filled with high-purity argon, mix them evenly to prepare a solvent, and then add the solute LiPF ₆ to a concentration of 1 mol/L of LiPF ₆ to prepare EC-DMC-LiPF ₆ Electrolyte system, then add the lithium ion secondary battery electrolyte additive 4 prepared in Example 4 to the EC-DMC-LiPF ₆ electrolyte system, mix well, and make electrolyte 6; In electrolyte 6, with When the mass of the electrolyte 6 is 100%, the addition amount of the electrolyte additive 4 for the lithium ion secondary battery is 5% wt of the mass of the electrolyte 6 .

Embodiment eleven:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 1a is carried out, specifically:

(1) Preparation of positive electrode: The ternary material (NCM111) is used as the active material, and the conductive agent activated carbon (Super P) and the binder polyvinylidene fluoride (PVDF) are uniformly mixed in nitrogen methyl pyrrolidone (NMP) solution. The mass ratio of active material, activated carbon (SuperP) and binder is 80:10:10, respectively, and then coated and pressed on aluminum foil to obtain a positive electrode;

(2) Selection of negative electrode: take metal lithium sheet as negative electrode;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 1 prepared in Example 5 was used, and the positive electrode and the negative electrode were used to assemble a CR2032 button lithium battery as the lithium battery 1a.

Embodiment 12:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 2a is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as embodiment eleven;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 2 prepared in Example 6 was used, and the positive electrode and the negative electrode were used to assemble a CR2032 button lithium battery as the lithium battery 2a.

Embodiment thirteen:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 3a is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as embodiment eleven;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 3 prepared in Example 7 was used, and the positive electrode and the negative electrode were used to assemble a CR2032 button lithium battery, which was used as the lithium battery 3a.

Embodiment fourteen:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 4a is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as embodiment eleven;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 4 prepared in Example 8 was used, and the positive electrode and the negative electrode were used to assemble a CR2032 button lithium battery, which was used as the lithium battery 4a.

Embodiment fifteen:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 5a is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as embodiment eleven;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 5 prepared in Example 9 was used, and a positive electrode and a negative electrode were used to assemble a CR2032 button lithium battery, which was used as the lithium battery 5a.

Embodiment sixteen:

This embodiment is basically the same as the previous embodiment, and the special features are:

In this embodiment, the preparation of the lithium battery 6a is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as embodiment eleven;

(3) Assembly and preparation of lithium battery: A glass fiber separator was used, the electrolyte 6 prepared in Example 10 was used, and a positive electrode and a negative electrode were used to assemble a CR2032 button lithium battery as the lithium battery 6a.

Comparative ratio:

In this comparative example, the preparation of the control battery is carried out, specifically:

(1) preparation of positive electrode: same as embodiment eleven;

(2) selection of negative pole: same as Embodiment 11;

(3) Assembly and preparation of lithium battery: take a certain amount of electrolyte HR-8335 (Shandong Hairong) in a glove box filled with high-purity argon gas, and use it as a comparison sample of electrolyte; use a glass fiber separator and use electrolyte HR -8335, using the positive and negative electrodes, assembled into a CR2032 button lithium battery as a control battery.

Electrochemical performance test analysis:

The batteries prepared in Examples 11-16 and Comparative Examples were tested for electrochemical performance on a LAND-CT2001A charge-discharge tester.

During the charge-discharge test, specifically, within the voltage range of 2.5-4.6V, the batteries prepared in Examples 11 to 16 and Comparative Then, under the current of 0.5C, the battery is discharged with constant current, and the cut-off voltage is 2.5V. This is a cycle, and other conditions remain unchanged for 50 weeks. The electrochemical performance test results are shown in Table 1.

Table 1. Electrochemical performance test discharge capacity comparison table of batteries prepared in Examples 11-16 and Comparative Examples

Discharge capacity (mAhg^-1) control battery 1a 2a 3a 4a 5a 6a the first week 193 195 197 196 187 193 194 Week 50 151 167 173 179 156 169 164 retention rate 78.2% 85.6% 87.8% 91.3% 83.4% 87.6% 84.5%

It can be seen from Table 1 that with the electrolyte additive of the present application, the capacity retention rate is still high after 50 cycles of cycling, which can effectively improve the high-potential cycle performance of the lithium ion battery. In the control cells, the cells had lower capacity retention and poorer high-potential cycling performance after 50 cycles of cycling.

The above embodiments of the present invention prepare a lithium ion electrolyte additive combination system and a lithium ion battery electrolyte containing the additive system. The additive combination includes: propylene carbonate-like derivatives and diisocyanate-like compounds. The additive combination system of the present invention is suitable for lithium ion secondary batteries with charging potential higher than 4.2V (vs. Li/Li ⁺ ). Propylene carbonate-like derivatives, such as mentioned ethylene ethylene carbonate, are electrochemically oxidized at the positive electrode at potentials above 4.2 V (vs. Li/Li ⁺ ) to a cation with an onium ion at one end (ref) , can form a stable passivation film on the positive electrode through nucleophilic addition reaction with HDI, prevent further oxidative decomposition of the electrolyte, and effectively improve the cycle performance and rate performance of the battery. The discharge capacity of the ternary cathode material NCM111 is still high at the potential of 4.6V (vs. Li/Li ⁺ ), but the common carbonate electrolyte is easily oxidized and decomposed at this potential, which reduces the high-potential cycle performance of the battery. Using this electrolyte additive system, when the voltage is higher than 4.2V, a passivation film can be formed on the surface of the positive electrode material, which can effectively improve the high-potential cycle performance of the lithium-ion battery.

The embodiments of the present invention have been described above, but the present invention is not limited to the above-mentioned embodiments, and various changes can also be made according to the purpose of the invention and creation of the present invention. Modifications, substitutions, combinations or simplifications should all be equivalent substitution methods, as long as they meet the purpose of the present invention, as long as they do not deviate from the technical principles and inventive concepts of the lithium ion secondary battery electrolyte additives, electrolytes and their applications of the present invention , all belong to the protection scope of the present invention.

Claims (5)

1. a lithium ion secondary battery electrolyte additive, it is characterized in that: form a lithium ion secondary battery electrolyte additive system by two kinds of components of propylene carbonate compound A and diisocyanate organic matter B, according to the total amount of electrolyte additive. Based on 100% by weight, the electrolyte additive contains 1-99 wt.% of propylene carbonate derivative A and 1-99 wt.% of diisocyanate organic compound B; The structural formula of the diisocyanate organic substance B is: R-[N=C=O]n, wherein, n≥2, R is an alkyl bridging group with a carbon content greater than 1; The propylene carbonate derivative A adopts styrene carbonate or 2,3-butanediol carbonate; The diisocyanate-based organic substance B adopts hexamethylene diisocyanate; the mass ratio of the propylene carbonate-like derivative A and the diisocyanate-based organic substance B is (1-9):1. 2. An electrolyte solution containing the lithium ion secondary battery electrolyte solution additive of claim 1, comprising an electrolyte and a solvent, characterized in that: the electrolyte contains lithium salt and lithium ion secondary battery electrolyte solution additive; Described solvent adopts ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dimethyl sulfite, vinylene carbonate, methyl propyl carbonate, ethyl acetate, methyl acetate Any one or any mixture of ester, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate and propyl acetate; In the electrolyte, the lithium salt is any one or any of several salts of LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiODFB and LiN(SO ₂ CF ₃ ) ₂ . 3. The electrolyte according to claim 2, wherein the content of the electrolyte additive for lithium ion secondary batteries in the electrolyte is 0.002-10 wt.% based on the total mass of the electrolyte being 100%. 4. The electrolyte according to claim 2, wherein the content of the electrolyte additive for lithium ion secondary batteries in the electrolyte is 5-10wt.%, taking the total mass of the electrolyte as 100%. 5. an application of the described electrolyte of claim 2, is characterized in that: the electrolyte that adopts this additive combination can be applied to the lithium ion battery that the charging potential is not less than 4.6V; The positive electrode material of the lithium ion battery is a lithium-containing ternary oxide material NCM; The negative electrode material of the electrolyte of the lithium ion secondary battery is graphite.